A jet engine is for example comprised of a fan assembly, a high-pressure compressor, a combustor, a turbine and other assemblies, in the order from the foremost stage to the rear. Ambient air sucked by the fan assembly is compressed and introduced into the combustor by the high-pressure compressor, and is there mixed with fuel and then used for combustion. High-temperature gas flow at high pressure generated by the combustor is introduced into the turbine and there energy is extracted from the gas flow.
As directly sucking ambient air, the fan assembly is exposed to hard impact by foreign matters impinging thereon. In particular leading edges of fan blades require excellent impact resistance. One of solutions to requirement for such localized impact resistance may be, for example, to add reinforcements having high impact resistance limitedly to the leading edges of the fan blades.
On the other hand, fan blades require not-simple three-dimensional surfaces in order to realize good aerodynamic properties, and thus surfaces of the leading edge reinforcements are required to be in conformity therewith. However, most of materials having high impact resistance have poor workability and it is even hard to carry out cold working on these materials. How to execute such three-dimensional surface machining is a technical problem. Further, in such reinforcements, required thickness in view of impact resistance varies from its most leading portion to peripheral portions. In a point about how a sectional profile according to a required thickness distribution is given to its final shape, technical issues may exist.
More specifically, consistence of high impact resistance and three-dimensional surface machinability is for itself a challenging technical problem.
Japanese Patent Unexamined Publication 2005-256838 discloses a production method of leading edges of fan blades using superplastic forming. This art applies diffusion bonding instead of cold bending to formation of an envelope structure for being served to superplastic forming, thereby overcoming the problem in machining of complex shapes such as the leading edges of the fan blades.